I'll go ahead and add my two cents here, since I do conflict mediation and crisis resolution on a daily basis.
First, a little information about the mechanics behind a reported post: when a post or pm is reported it creates a thread in the Administrator/Moderator forum with a link to the post (but not pm) and quotes the post in question. It then also posts the nature of the report (i.e. "this is spam") which is inputted by the reporter.
The point should be made that just because someone gets reported (for whatever reason) does not necessarily mean that any administrative action will be taken against the person being reported.
Many times, depending on the nature of the reported post, an unofficial warning will be sent to the poster (if necessary). "Tone it down" or "Keep in mind this is a family friendly environment" etc. If more posts come that require further action a temporary ban might be in order (3 days is typical).
In the case of pm's, if someone is bugging you for freebies or giveaways you can simply report it. It creates the record and more than likely, nothing will happen (unless specific forum rules are also violated in that pm). But the important part is, a record is made. Then, when the second record and third record come in there is a document trail that can be looked out that isn't so circumstantial or subjective.
Anyways, that is a lot of words that most people probably don't care about; but for those of you in college that lived in residence halls and had resident assistants might appreciate this analogy: your neighbors next door are loud. A RA from another floor comes and tells them to be quiet but doesn't file an incident report. The next night a different RA comes and tells them to be quiet and also does not submit a report. This goes on and on for a few more nights. Obviously there is a bigger problem but there is no paperwork to use as evidence because nothing official has been done. So when the hall directors get involved with this problem they have to start at square one.